Slicing and soaking in milk reduces the pee smell a lot. I've also read that to roll the slices in baking powder then soak in salted water for an hour will remove the smell but I haven't tried that as milk works fine for me.

Do you like soup? A Filipino lady I knew years ago used to make a soup of chicken broth, with finely sliced shallots cooked in it, slices of grilled and skinned red peppers and when they were softened, she added sliced soaked kidneys which were simmered until just cooked, then she tipped in loads of chopped coriander (cilantro) and grated lime rind. It was awesome....